Radio signals may be transmitted from a terrestrial (or ground-based) transmitter or from a non-terrestrial transmitter, such as a satellite. Certain frequencies on the electromagnetic spectrum have been dedicated to satellite transmissions, by international agreement. In the case of direct broadcast satellite service (“DBS”), for example, the 1985 Regional Administrative Radio Conference ARC) of the International Telecommunication Union established the spectrum for DBS at 17.3-17.8 GHz for the uplink and 12.2-12.7 GHz for the downlink in ITU Region 2, the Western Hemisphere. In all, thirty-two frequencies were allotted at each of eight orbital locations set aside for DBS in the United States. Significantly, the RARC also made provisions for the reuse of the satellite-allocated frequencies. See Mead, Donald C., Direct Broadcast Satellite Communications, pages 21-22 (2000).
Public policy favors the fullest and most efficient use of spectrum. Reuse of satellite-allocated frequencies by a terrestrial system would provide increased availability of video programming and data, as well as an alternative to cable and satellite systems. Accordingly, a terrestrial wireless system capable of transmitting multiple channels of broadband data and video to homes and places of business and/or providing a return link for data and video would be very useful. Previous approaches for increasing availability of video and broadband data have involved satellite reception of video and broadband data in combination with reception of video and broadband data from other sources. Such system are either inefficient or entirely ineffective.
For example, Armbruster, in U.S. Pat. No. 5,774,194, discloses a terrestrial and satellite television reception tuner which is used in common for both one-way terrestrial and satellite television reception. The tuner incorporates a second mixing stage which is switched as a mixer for signal conversion into a second intermediate frequency during terrestrial television reception and is switched as a component of a FM-PLL demodulator during satellite television reception. The tuner is disclosed as being particularly suitable for television receivers and video recorders which receive signals from both terrestrial antenna-signal source and from a satellite antenna-signal source.
Do, in U.S. Pat. No. 5,966,187, discloses a device for receiving a one-way digital broadcasting satellite (DBS) signal, which includes a controller for generating a first signal for selecting a program guide signal included in a DBS signal and a second signal for selecting one of a plurality of programs which are included in the program guide signal, in response to input of certain key signals, a decoder for decoding the program guide signal in response to the first signal, a storing unit for separating and storing the decoded program guide signals as position data, channel data and video data, a signal compressing unit for compressing the video data corresponding the second signal, a mixer for mixing the decoded program guide signal as a main screen signal with the compressed video data as a sub-screen signal, and a display unit for displaying the signal mixed by the mixer. The device is disclosed as receiving a DBS signal and a TV signal.
Tawil, in U.S. Pat. No. 5,483,663, discloses an apparatus for receiving one-way local programming and direct broadcast satellite transmissions, which includes receiver for receiving converted local channel signals in a first frequency band. Tawil discloses that the first frequency band is contained within a satellite broadcast frequency band in which the direct broadcast satellite signals are transmitted. Specifically, the apparatus disclosed by Tawil includes at each user or subscriber location, a first antenna for receiving the converted local channel signals from a terrestrial transmitter and a second antenna for receiving direct broadcast satellite channel signals from a satellite. The disclosed apparatus further includes a combiner for combining the converted local channel signals in the direct broadcast satellite channel signals on a single propagation path. A signal processor/decoder processes the combined signals on the single propagation path to produce a desired channel output to drive a television set. It is disclosed that to the processor/decoder the combined channel signal appears as if it had been all broadcast directly from the satellite and therefore, the apparatus requires no additional receiver for receiving local programming alone with regional and national programming received via satellite.
Tawil et al., in U.S. Pat. Nos. 5,761,605 and 6,169,878, disclose an apparatus and method for simultaneously receiving one-way satellite and terrestrial signals. The disclosed apparatus includes a first antenna at a user location which receives signals at a first frequency where the signals are traveling only within a first directional reception range as measured from a centerline of the first antenna. The first antenna has its centerline aligned to receive direct broadcast satellite signals transmitted from a satellite in geostationary satellite orbit about the earth. A second antenna is disclosed as being at the user location to receive signals at the first frequency where the signals are traveling only within a second directional reception range as measured from a centerline of the second antenna. Further, the second antenna is aligned to receive signals transmitted at the first frequency from a terrestrial transmitting location remote from the user location. According to the reference, a satellite's position is such with respect to the user location that the satellite transmits directionally in directions outside of the directional reception range of the second antenna.
Wild et al., in U.S. Pat. No. 5,862,480, disclose a method and apparatus for managing service accessibility between differing radio telecommunications networks. The disclosed method allows a network and a multi-network system to obtain access information for a subscriber unit. The method involves requesting access information from an access server which determines whether a group to which the subscriber unit belongs can access the network or other networks from the subscriber unit location. The reference discloses the applicability of the network and apparatus in enabling hand-offs between overlapping networks. In particular, FIG. 2 illustrates a satellite cellular foot print with an overlapping terrestrial cellular foot print. The disclosed cellular satellite foot print is STET by satellite and includes satellite cells while the terrestrial cellular foot print is projected by terrestrial antenna and includes terrestrial cells.
Martinez et al., in U.S. Pat. No. 5,584,046, disclose a method and apparatus for spectrum sharing between one-way satellite and terrestrial broadcasting services using temporal spatial synchronization. The disclosed system and method uses time division multiple access between two types of service providers to achieve synchronization. The reference discloses that satellite and terrestrial broadcasting services are assigned geographic cell boundaries to prevent conflicting simultaneous use of allocated spectrum. The spatial synchronization of cell boundaries can occur before hand by agreement between the users of the satellite and terrestrial services. This spatial synchronization may conform to geographic as well as political boundaries. In the disclosed system, satellite and terrestrial services are assigned time slots to use a given spectrum within a given area. Methods are also disclosed for synchronizing the time slots to prevent interference between the services.
Sakashita et al., in U.S. Pat. No. 4,939,789, discloses a signal receiver for terrestrial and satellite broadcasting. The disclosed signal receiver is capable of receiving and demodulating a satellite broadcasting signal which is an FM signal and a terrestrial broadcasting signal which is an AM signal. FM and AM signals are frequency-converted into signals having frequencies in a same intermediate frequency band by making common use of a radio frequency amplifier, a mixer, a local oscillator and an intermediate frequency filter. At the time of reception of an FM signal, the FM signal is demodulated in a phase-locked loop circuit, and a local oscillator is subjected to frequency modulation by a part of the demodulated signal, thereby constituting an FM negative feedback loop, and thus narrowing the occupied bandwidth of the FM signal. It is disclosed that at the time of reception of an FM signal, the phase-locked loop circuit is used to regenerate a carrier, and the output signal of the phase-locked loop circuit is input to a multiplier to affect synchronous detection of the input signal. It is further disclosed that at this time, the FM negative feedback to the local oscillator is utilized to affect automatic frequency control, thereby achieving stabilization of this synchronous detection.
The sharing of frequency bands between satellite and terrestrial stations has also been addressed. For example, the feasibility of frequency sharing between an earth station and a collocated radio relay station used for interconnection to the earth station has been addressed. See Potts, James B., “Feasibility of collocating a radio relay station with a sharing earth station”, COMSAT Technical Review, Vol. 2, No. 1, pages 205-219 (Spring 1972). According to Potts, the interference condition that results from collocation are tolerable, and since they are controlled by free space propagation, one can calculate the actual interference levels rather simply with a high degree of confidence. Potts discloses that it may also be feasible for the earth station to transmit in the shared frequency band. However, even if a viable system for combining satellite service with local programming is achieved, such a system generally requires additional complex and expensive equipment which undermines the economic feasibility of the system. Further, satellite systems such as DBS, occupy a portion of the electromagnetic spectrum which would otherwise be available for terrestrial signal transmissions. Given the limited available frequencies for terrestrial signal transmissions on the electromagnetic spectrum, as well as the advantages of avoiding the need for complex and costly receiving equipment, it would be desirable to provide a terrestrial radio system which would provide all of the national or regional television programming, such as that available typically only through satellite services, along with local television programming. Further, it would be desirable to have a terrestrial radio system which provides consumers with data transmission services, Internet services and two-way capabilities. Moreover, it would be desirable to provide a terrestrial radio system which reuses satellite-allocated frequencies without causing interference to satellite signals simultaneously transmitted at the same frequencies.